Hydraulic underreamer



R. C- BAKER HYDRAULIC UNDERREAMER Filed NOV. 26, 1946 July 8, 1952 r e m 3 6 m M V m b w E Patented July 8, 1952 HYDRAULIC UNDERREAMER Reuben C. Baker,..Coalinga, Calif., assignor to Baker ,Oil Tools,*Inc., Vernon, Calif.,"a corporation of California 1 Application November 26, 1946, Serial No. 712,383

' 3. Claims. 01. 255-76) The present invention relates to underreamers for enlarging the size 'of well' 'bores, and inore particularly to underreamers whose cutters are expanded tooperative positions by hydraulic Hereto fore,-plungers or piston devices for expanding underreamer l cuttersoutwardly have been restricted at their lower portions for the purposeof building up sufiicient back pressure on the high pressure side-Lot the piston plunger to force the cutters outwardly against the wallof the wellbore. The fluid expands through such restrictions and exh austs onto the cutters, to cleanse them of the formation material andremove' such material inthe drilling mud to the topofthewellbore. 7

Ithas been foundthat the expansion of the fluid through the jrestrictions or nozzles erodes the main body of the underreamer and lessens its life considerably, at a substantial economic loss. Notonly is the'bOdy eroded, butthe plunger device itself is fluid cut extensively.

Accordingly, it is an object of the present inventionto provide a hydraulic plungerv or piston in anunderreamer which exhausts fluid onto the cutters in such manner as to avoid cutting or eroding of the cutterbody,

Another object ,of the invention isto provide an underreamer embodyinga plunger or piston for expanding the underreamer cuttersin'which the wear in the plunger or piston itself is largely minimized. I r, 1 v

One'form which the invention may assume'is exemplified in the following description and illustrated by way of example in the accompanying drawings, in which: i V

Fig. 1 is a side elevation, partly in section, oi a rotary underramen U j I Fig. 2 is a longitudinal section taken'along the line22 nFig.1.

Fig. 3 is a cross-section-taken along the line 3-3onFig.1.

Underreamers of the typedisclose'd' in the drawings are described in detail in Unitd 'states Patent No. 1,857,616.' Theyinclude an elongate main supporting body provided with an upper threaded box ll attachable to the lower end of a string of drill pipe 12 'or the like, by means of which the underreamer is lowered in the well bore and rotated in the performance of its under reaming operation. The'body has a"c'entral'l'ongitudinal passage [3 therethrougli merging into diametrically opposed elongate slots l 4 opening outwardly 'orthe lq dyr n a'ir o utter piaues I 5 of tha drag type are i'rioiidblttitliifl'tli slots.

being mounted upon a'hinge pin l6 extending through the body and across its passage 13.

The cutters [5 have an initial downward'position substantially completely retracted'within the confines'o'f the body In, and are swingable outwardly in opposite directions to extend'beyond the periphery of the body, occupying-a generally horizontal position, with their upper sides I511 engaging the upper shoulders I! of the longitudinal slots I4. A second set of longitudinal slots i B extend upwardly to one side of and above the stop shoulders I! at the ends or the "main slots to provide passages through which drilling fluid may pass for discharge 'onto'the cutter blades l5, infamannelr' tobe hereinaftendscribed. The blades are swingable inwardly and outwardly of the body slots I4 in response 'to' upward anddownwardmovement of an operating plunger I9 slidable within the central passage 13 of the main body. This plunger inoludesia'tubu lar plunger body 20' having 'a transverse hole through depending legs 2| in its lower endfo'r receiving a pivot pin 22, in which the upperends of a pair of links 23arepivotally mountd between the legs. The lower end o f each link is pivotally attached to a cutter: blade I 5 by means of a pin 24. It is to be noted that'the links 23 are pivoted to the blades on oppositesi'des Of-the hinge pin I6, in order that :downward movement of the plunger l9 pivots the blades -15 oppositely in upward and outward directions. "Such outward movement may continue, asaforeinentioned, until the blades occupy horizontal positions in contact with the body shoulders ll."

The upper end of the body passage 13 is enlarged in diameter to form a cylinder 25 .slidably receiving the upper piston portion 26fof the plunger, which is also enlarged to a diameter greater than the lower plunger body portion 20. A plurality of piston ringsZl, or rubber or similar material, are mounted on the pistonior slidable sealing engagement with the wall of. the cylinder'25 to prevent leakage in both directions around the? piston. Aspring 28 encircles the smaller'diameter plunger body portion 2.0, one end engaging the lower end 29 of the cylinder and its other end engaging the piston 26, This spring is under ,compressionand tends to elevate the plunger l9 and. retract. and maintain the blades 15 in their inward position within the confines ofthebodyllh The plunger I9 is movable downwardly ,andthe blades expanded outwardly by the pressure of fluid, like drilling mud, pumped downwardly through the string of drill pipe l2 and acting upon the piston 26. Since it is desired to discharge the drilling fluid onto the cutters I5 to maintain them free of detritus, the fluid continues downwardly through a central passage 38 in the plunger IQ for discharge in opposite directions through elongate slots 3! in the lower portionof the plunger body and through the upper body slots [8 onto the forward cutting faces of the cutter blades. In view of this discharge of fluid, an orifice or restriction is provided in the plunger passage 39 to enable a back pressure to be built up on the high pressure side of the piston 26 suflicient in value to overcome the compressive force of the spring 28, shift the plunger I9 downwardly, and swing the blades [5 outwardly, through the agency of the pin and link connections 22, 23, 2% between the plunger 19 and blades l5. In prior devices, such restriction was placed in the lower portion of the plunger,

the fluid expanding outwardly through such restricted portion at a comparatively high velocity and producing a cutting action on the side body walls of the slots [8 and on the blades themselves, shortening the life of the parts consider ably.

In the device under consideration and illustrated in the drawings, the restriction for producing the back pressure on the high pressure side of the piston is placed at the upper portion of the plunger and the fluid expansion and lowering of its velocity takes place within the plunger body itself. Specifically, a restricted orifice means 32 is threaded within the piston 26, the passage 33 at the upper end of the orifice being of such diameter as to insure the building up of sufficient back pressure within the cylinder space .25 at the upper end of the body I0. I The orifice has a depending skirt 34, of a much greater internal diameter than the diameter of the orifice passage 33, in which a circulation bean or bushing 35 is placed, preferably of a hard metal, such as tungsten carbide. This bushing is clamped between a shoulder 36 at the upper end of the orifice 32 and a spacer sleeve 31 whose lower end rests upon an internal shoulder 38 in the plunger body 26, whose upper end engages the lower end of the bushing 35, and whose intermediate shoulder 39 engages the lower end of the orifice skirt 34. It is to be noted that the internal diameter of the hard metal bushing or bean 35 is much greater than the diameter of the orifice passage 33 and that the internal diameter of the spacer sleeve 31 is no less than the internal diameter of the hard metal bushing 35. If desired, the inner wall 40 of the spacer sleeve 3'! may flare outwardly in a downward direction to simulate a Venturi nozzle.

The passage 30 through the plunger body 20 between the lower end of the spacer sleeve 3'! and the longitudinal slots 3! is at least equal in diameter to the internal diameter of the spacer sleeve itself, and the elongate diametrically opposite slots 3| in the plunger body have a crosssectional area at least as great as the area through the plunger body below the spacer sleeve.

If desired, a circulation screen 4| may extend upwardly from the restricted orifice passage 33, having spaced openings 42 to prevent passage of comparatively large particles suspended in the drilling mud into the orifice, which might plug same. This screen portion, however, need not be employed, especially where relatively clean drilling muds are circulated down through the drill pipe.

The underreamer is lowered through a. well casing with the plunger [9 held in an upward direction by the compressed spring 28, which insures the inward retracted position of the blades l5 within the confines of the body 10. When the desired position below the casing shoe (not shown), is reached at which an underreaming operation is to occur, the drill pipe [2 and underreamer are rotated and pressure imposed upon the fluid in the drill pipe. Such fluid acts upon the piston 26 and forces it downwardly against I the action of the spring 28 to expand the blades I5 outwardly to their fullest extent. A back pressure is built up by virtue of the restricted orifice 32 in the upper portion of the plunger assembly, fluid passing through the restricted orifice passage 33 and expanding outwardly within the hard metal circulation bushing 35 into its passage. The fluid then flows through the spacer sleeve 31 and the plunger body passage 30 therebelow for exhaustion through the opposed longitudinal slots 3| and body slots [8 onto the cutter blades l5, cleaning the latter of detritus and flushing it in the drilling mud to the top of the well bore.

It is to be noted that the fluid increases considerably in velocity in passing through the restricted passage 33 in the upper orifice, and that upon leaving such passage it expands and assumes a much lower velocity, in view of the much larger area through'the hard metal bushing passage 35. Such expansion to a lower pressure is ordinarily associated with fluid cutting of the parts contacted by the hydraulic stream. However, since the eroding or cutting force of the fluid stream is against the hard metal bean 35, very little harm to it results,since it is well able to withstand the erosive forces. The fluid has lost much of its high velocity upon expanding into the circulation bean and then proceeds downwardly through the spacer sleeve 37 and outwardly through the opposed plunger body slots 3 I, all at a comparatively low velocity. The fluid undergoes no expansion in passing outwardly through the slots 3! and impinging on the sides of the body slots 18 and the cutter blades l5 themselves, and as a consequence, does not erode the side walls of the body slots.

Any erosive wear that might occur takes place within the plunger bean 35 itself and within the spacer sleeve 31. These parts arerelativelyinexpensive and may be easily replaced. For that matter, the occurrence of any erosive wear in the entire plunger body l9 involves only a'comparatively inexpensive part which can be easily replaced.

It is, accordingly, apparent that a plunger device for a hydraulic underrearner has been devised in which most, if not all, of the wear or abrading action attributable to the circulating fluid occurs within the plunger'itself, which is a comparatively simple part to manufacture and one which is readily replaceable. The underreamer body itself is not subjected to the velocity action of an expanding fluid stream and its life is prolonged substantially.

While I have shown the preferred form of my invention, it is to be understood that various changes may be made inits construction by those skilled in the art without departing. from the spirit of the invention. as defined in the appended claims.

Having thus described my invention, what I claim and desire to secureby' Letters Patent is:

l An underreamer, including a body adapted to be attached to a drill string and having a longitudinally extending slot therein, expansible cutter means carried by said body within said slot, means for expanding said cutter means oute wardly comprising a tubular plunger in said body having longitudinally elongate outlet means in alignment with said slot for discharging fluid through said slot directly upon said cutter means, means on the plunger providing a flow restricting orifice in the path of fluid flow through said plunger through which all of the fluid moving through said plunger must pass, said orifice being disposed and spaced a considerable longitudinal distance upstream from said outlet means, said plunger being imperforate between said orifice and outlet means, said plunger having an internal cross-sectional area throughout its length between said orifice and said outlet means substantially greater than the internal cross-sectional area of said orifice but no greater ing orifice in the path of fluid flow through said plunger through which all of the fluid moving through said plunger must pass, said orifice being disposed and spaced a considerable longitudinal distance upstream from said outlets, said plunger being imperforate between said orifice and outlets, said plunger having an internal cross-sectional area throughout its length between said orifice and outlets substantially greater than the crosssectional area of said orifice but no greater than the total area through said outlets.

3. An underreamer, including a body adapted to be attached to a drill string and having a longitudinally extending slot therein, expansible cutter means carried by said body within said slot, means for expanding said cutter means outwardly comprising a tubular plunger in said body having longitudinally elongate outlet means in alignment with said slot for discharging fluid through said slot directly upon said cutter means, means on the plunger providing a flow restricting orifice in the path of fluid flow through said plunger through which all of the fluid moving through said plunger must pass, said orifice be ing disposed and spaced a considerable longitudinal distance upstream from said outlet means, erosion resisting sleeve means in the plunger adjacent and on the downstream side of said orifice means, said plunger being imperforate between said orifice and outlet means, said plunger and sleeve means having internal crosssectional areas throughout their lengths between said orifice and said outlet means substantially greater than the internal cross-sectional area of said orifice but no greater than the total area through said outlet means.

REUBEN C. BAKER.

REFERENCES CITED The following references are-of record in the file of this patent:

UNITED STATES PATENTS Number Name Date 1,981,262 Burt Nov. 20, 1934 1,993,182 Santiago Mar. 5, 1935 2,072,859 Grant Mar. 9, 1937 2,203,998 OGrady June 11, 1940 2,238 998 Grant Apr. 22, 1941' 2,408,892 Stokes Oct, 8, 1946 

